On-board units for road toll systems are also known as OBUs. OBUs that can determine and fix their position themselves, for example, using a satellite navigation receiver, are currently available in two different embodiments. So-called “thick client” OBUs use stored toll maps as the basis for calculating location-anonymised toll data from their position-fix data, and send this toll data, for example, via a mobile telecommunications network to a control centre of the road toll system, a procedure that requires expensive distribution of the toll maps to the OBUs and a large amount of processing power in the OBUs. In contrast, so-called “thin client” OBUs do not evaluate their position-fix data themselves but send this data “raw” to a control centre, which in turn performs “map matching” to generate toll data therefrom. Thin client OBUs therefore have a substantially simpler and cheaper design, but present a problem from the data-protection viewpoint, because the control centre of the road toll system gains knowledge of the full set of position-fix data (“movement profile”) of an OBU.
Therefore it has already been proposed in WO 2008/000227 to send the position-fix data of a thin client OBU under an anonymised sender identifier to a special toll calculation server, which performs the map matching and sends back to the OBU location-anonymised toll data, which the OBU then transmits to the control centre. WO 2009/001303 describes a similar type of solution.
The known data protection solutions have the disadvantage that they cause higher levels of data traffic in the road toll system and/or mobile telecommunications system and require additional data transmissions by the OBU, which also results in a correspondingly higher power consumption of the OBU.